The technique of electrolysing water in the presence of an electrolyte such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) to liberate hydrogen and oxygen gas (H.sub.2, O.sub.2) is well known. The process involves applying a DC potential difference between two or more anode/cathode electrode pairs and delivering the minimum energy required to break the H--O bonds (i.e. 68.3 kcal per mole @ STP). The gases are produced in the stoichiometric proportions for O.sub.2 :H.sub.2 of 1:2 liberated respectively from the anode (+) and cathode (-).
Reference can be made to the following texts: "Modern Electrochemistry, Volume 2, John O'M. Bockris and Amulya K. N. Reddy, Plenum Publishing Corporation", "Electro-Chemical Science, J. O'M. Bockris and D. M. Drazic, Taylor and Francis Limited" and "Fuel Cells, Their Electrochemistry, J. O'M. Bockris and S. Srinivasan, McGraw-Hill Book Company".
A discussion of experimental work in relation to electrolysis processes can be obtained from "Hydrogen Energy, Part A, Hydrogen Economy Miami Energy Conference, Miami Beach, Fla., 1974, edited by T. Nejat Veziroglu, Plenum Press". The papers presented by J. O'M. Bockris on pages 371 to 379, by F. C. Jensen and F. H. Schubert on pages 425 to 439 and by John B. Pangborn and John C. Sharer on pages 499 to 508 are of particular relevance.
On a macro-scale, the amount of gas produced depends upon a number of variables, including the type and concentration of the electrolytic solution used, the anode/cathode electrode pair surface area, the electrolytic resistance (equating to ionic conductivity, which is a function of temperature), achievable current density and anode/cathode potential difference. The total energy delivered must be sufficient to disassociate the water ions to generate hydrogen and oxygen gases, yet avoid plating (oxidation/reduction) of the metallic or conductive non-metallic materials from which the electrodes are constructed.
Reference also is made to prior art Australian Patent No.487062 now U.S Pat. No. 4,014,797 filed herein on Mar. 5, 1996 in the name of Yull Brown, that discloses an electrolysis cell arrangement to produce hydrogen and oxygen on demand, together with a safety device preventing the generation of excess pressure of the liberated gases. FIG. 2 of the Brown patent shows a number of electrodes (20a,20b) in a series electrical arrangement between two terminals (22), across which a voltage is applied. The cell (20) produces a gas volumetric flow rate output, and if that output is insufficient for a particular application, then a larger number of individual cell units must be provided, all electrically connected in series. The end result is a large structure to be supported.
It is also not possible to produce high gas flow rates (of the order of 10,000 liters per hour) on demand from the prior art apparatus without the use of expensive and complicated equipment, and even then the equipment suffers from low efficiencies in the conversion of electrical energy to generate the hydrogen and oxygen gases. Thus the large scale commercial implementation of such apparatus is not economically viable.
Admixed hydrogen and oxygen gases (or hydroxy gas) are used as a thermal source when burnt in a stream, for example, in furnaces. Hydrogen alone is used for atomic cutting and often for atomic welding, although the device described in the Brown patent performed atomic welding with admixed hydrogen and oxygen. Recent industry practice clearly exemplifies that the presence of oxygen in a plasma arc causes severe oxidation of the tungsten electrodes.
One of the problems experienced in implementing these applications is the need to incorporate electrical switchgear to transform mains supply voltages to a level suitable for a bank of electrolysis cells (i.e. by step-down transformers). The resulting completed arrangement is inefficient electrically and cumbersome, and also can be expensive if precise voltage and current regulation (hence gas flow regulation) is required.
Combusted hydrogen and oxygen gases mixed into a single stream burn at a very high temperature, typically of the order of 6000.degree. C. Hydrogen/oxygen welding sets are generally known to comprise of a welding tip or hand piece connected by a dual gas hose to separate supplies of oxygen and hydrogen.
There are four other common types of welding apparatus and techniques in use; these are oxy-acetylene welding, electric arc welding, MIG (metal-inert-gas)/TIG (tungsten-inert-gas) systems and plasma cutting.
It is estimated that more than 100,000 oxy-acetylene sets are used in Australia. Of those, approximately 70% are used primarily for the cutting of metals, with the remainder being used as a heat source, for fusion welding of sheet metal, brazing, silver soldering and the like. Typically oxy-acetylene sets can weld thicknesses of metal between 0.5 mm to 2 mm. Further, thicknesses up to 140 mm can be cut, but only where the steel contains a high percentage of iron. The reason for this is that the iron and the oxygen are required to support the oxidation process which induces the cutting effect. The acetylene gas provides the initial temperature to start the oxidation reaction, being typically 850.degree. C. Oxy-acetylene sets require a bottled supply of both acetylene and oxygen gas, hence the bottles must be bought or hired, then continually maintained and refilled with use.
Electric arc welding is a method used for welding metals of greater than 1.5 mm thickness. The principle of operation is that a hand piece is supplied with a consumable electrode, and the work piece forms the other electrode. An AC or DC potential difference is created between the electrodes, thus causing an arc to be struck when the hand piece is brought into proximity of the work piece. The arc can be used to fuse or weld metal pieces together.
MIG systems are based around a continuous wire feed system. In one known arrangement, the consumable wire is shrouded by argon gas (or a plasma), which typically is sourced from a bottled supply. TIG systems, on the other hand, require the filler wire to be hand-fed into the weld pool. MIG/TIG systems can weld from between 1 mm to 20 mm thicknesses of metals, and typically stainless steel, aluminium, mild steel and the like. Reference can be made to a text "The Science and Practice of Welding, Volume 2, A. C. Davies, Cambridge University Press" in respect of plasma MIG processes.
Plasma cutting is a method of cutting by introducing compressed air (comprising predominantly nitrogen) to a DC electric arc, thereby producing very high temperatures (about 15,000.degree. C.) and so stripping electrons from the nitrogen nucleus to form a high temperature plasma. This plasma can be utilised to cut ferrous and non-ferrous materials such as mild steel, stainless steel, copper, brass and aluminium. Available plasma cutters can cut up to a 25 mm thickness and have the advantage of not requiring bottled gas but rather utilise free air. Reference can be made to the text "Gas Shielded Arc Welding, N. J. Henthorne and R. W. Chadwick, Newnes Technical Books" in respect of plasma cutting.
As follows from the discussion of the prior art, no one unit or system has the capability of performing all welding and cutting functions, and typically, one of the systems already described would be chosen over another for any particular job. This then requires that metal workers or other metal trades industry manufacturers must purchase and maintain a number of different types of welding units in order to have the capability to handle any job on demand. The costs associated with the purchase of replacement bottled gas also are very high.